1. Field of the Invention
The present invention relates to a device for injecting light into an optical wave guide, by means of which a focused light beam is aligned by a manipulator, the injection end of the optical wave guide to be coupled being connected to an optical system. Via such a device, the system is adjusted to maximum injection efficiency, i.e., maximum transmission efficiency of the laser beam into the optical wave guide and fixing of the adjusted positions obtained during coupler adjustment, so that these positions remain permanently stable.
2. Description of the Background Art
Methods for transmitting information and energy by conducting light via optical fibers have been known for approximately 40 years.
Transmission systems of this type are based on optical fibers made of silica glass or of other suitable materials, having a radially variable refractive index curve and shielding cladding for the purpose of obtaining optical wave guides along which light energy may be conducted in a controlled manner. The optical fibers are extremely thin (<0.01 mm core diameter) and must be connected to light sources and receivers in a functionally reliable manner having few transmission losses. The best possible coupling between two fibers is achieved by placing the smoothly polished ends of the fibers to be coupled flat against one another. This ideal state is achievable only using high-precision equipment and is poorly suited for practical applications for cost reasons. Designs of this type are therefore not suitable for detachable connections.
For the purpose of detachably coupling a light beam transmission system, a method is know for injecting a collimated beam into an optical wave guide using focusing lenses or focusing lens systems.
To achieve an extremely low-loss transmission at a fiber coupling point, it is necessary to bring the axis of the incoming light beam into highly precise axial alignment with the axis of the optical conductor.
Different approaches to this problem are known.
A plug connector is known from U.S. Pat. No. 4,087,155, in which the fibers are coupled without an objective being connected therebetween. The fiber ends each rest between three elastically mounted, movable bearings.
In U.S. Pat. No. 4,296,999, the fiber coupling is described on the basis of two precisely coaxially aligned couplers, the lens-fitted fiber ends being movable for the purpose of focusing in the Z direction.
A coupling device is also known according to DE 689 22 789 T2, by means of which a precise adjustment of the beam bundle is to be achieved by an apparatus in which the inclination of the fiber arrangement is adjusted relative to a spherical lens.
A device for the X/Y positioning of an optical element is known from U.S. Pat. No. 5,029,791, in which movement in two coordinate directions is made possible by screw mechanisms.
An arrangement for connecting and aligning two optical components is specified in EP 708 347 A1, which corresponds to U.S. Pat. No. 5,673,348, in which the positioning precision is achieved by a differential thread.
Precise, low-friction guidance and precise fixing of the components are not achievable by these arrangements.
A holding device for optical components is further described in WO 92/02837 A1, this device including a mounting plate that has a spring arrangement that enables adjustment in two coordinate directions.
An arrangement for fine-adjustment of a component in the X/Y direction is specified in U.S. Pat. No. 4,691,586, in which a clearance-free adjusting movement is made possible by multiple parallel spring arrangements.
The precise movements required for injecting light into an optical wave guide, having three translatory and one rotatory degree of freedom, are not achievable by these arrangements.
The fiber couplers known from the related art make it possible to perform all necessary adjusting movements to the fibers. However, these principles have the disadvantage that the beam adjustment is very time-consuming, and corresponding experience is required because both the angular adjustment and the parallel movement in the known approaches take place within the X/Y plane, using the same adjusting means, and the different degrees of freedom are therefore not adjustable independently of each other. Consequently, residual errors in the adjustment must frequently be taken into account in order to shorten the adjustment operations.